In Ireland -a 'snake-oil' salesman : a committed 'Yes' man , no matter what the question or his previous views on that subject : a 'know-it-all' who will plausibly convince you of how right he is , while he fumbles in his greasy till , professionally hiding the fact that he knows nothing about the issue in question .
Usually ends up in a political career !

Too many to mention - also too libellous to do so !
" That fella up at the bar , there - he should be able to fix ya up . He's a wee bit of a gombeenman , but sure he's not the worst ... "